1. Field of the Invention
The present invention relates to a semiconductor light emitting device and a method of manufacturing the same, and more particularly, to a semiconductor light emitting device that can be manufactured by using a simple process and has excellent light extraction efficiency and a method of manufacturing the same that can obtain high reproducibility and high throughput.
2. Description of the Related Art
Semiconductor light emitting devices include materials that emit light. For example, light emitting diodes (LEDs) are devices that use diodes, to which semiconductors are bonded, convert energy generated by recombination of electrons and holes into light, and emit light. The semiconductor light emitting devices are being widely used as lighting, display devices, and light sources. In consideration of energy savings and the protection of environment, development of semiconductor light emitting devices has been expedited in that they can emit light having desired wavelength with low power consumption and prevent emission of environmental hazardous substances such as mercury.
In particular, the widespread use of cellular phone keypads, side viewers, and camera flashes, which use GaN-based light emitting diodes that have been actively developed and widely used in recent years, contributes to the active development of general illumination that uses light emitting diodes. Applications of the light emitting diodes, such as backlight units of large TVs, headlights of cars, and general illumination, have advanced from small portable products to large products having high power, high efficiency, and high reliability. Therefore, there has been a need for light sources that have characteristics appropriate for the corresponding products.
GaN-based LEDs have relatively high internal quantum efficiency and thus have high efficiency in terms of light generation. However, since the GaN-based LEDs have a higher refractive index (2.3 to 2.8) than peripheral materials, they have low light extraction efficiency. Therefore, in the general GaN-based LED, a considerable amount of light generated in a light emission layer cannot be extracted to the outside of the LED but disappears inside the LED.
In order to overcome said drawback, a technique that gives texture to a substrate or the surface corresponding to a path along which photoelectrons move or a technique that forms periodic patterns is introduced. However, the techniques are limited in terms of reproducibility and high throughput.
FIG. 1 is a cross-sectional view illustrating a semiconductor light emitting device 1 having a patterned surface according to the related art. The semiconductor light emitting device 1 includes a substrate 10, semiconductor layers 20 and 40 having different conductivities from each other, and an active layer 30 formed between the semiconductor layers 20 and 40 to generate light. In FIG. 1, the semiconductor layers 20 and 40 having different conductivities are referred to as a first conductivity-type semiconductor layer 20 and a second conductivity-type semiconductor layer 40.
Non-periodic roughening is performed on the surface of the semiconductor light emitting device 1, that is, an outer surface in a path along which the generated light moves. Since the non-periodic roughening is formed at the surface thereof, light moving inside the semiconductor light emitting device 1 finally satisfies extraction conditions and is extracted to the outside of the semiconductor light emitting device 1 (Lout). The non-periodic roughening is formed by various methods. For example, wet or dry etching may be performed by using a photo mask or a metal dot mask to obtain non-periodic roughening. In a case of the metal dot mask, a metal dot is formed at a high heat treatment temperature of 600° C. or more. When a metal dot is formed of Mg, Mg ions are deactivated, which increases Vf and reduces luminance. Further, it is difficult to remove the remnant of metal chloride formed at the etched surface during dry etching. In a case of photolithography technique, an etching mask can be relatively easily formed. However, expensive equipment needs to be used to form a pattern of a similar size to the wavelength.
Therefore, there has been a need for a method of simply improving light extraction efficiency of the semiconductor light emitting device at low costs.